Effect Of Different Surfactants Research Articles

Theoretical study on the influence of three different surfactants on the binding of laccase with bisphenol A

Laccase catalyzes the formation of phenoxyl radicals as an intermediate in Bisphenol A (BPA) degradation, and certain surfactants can affect the effectiveness of laccase in removing BPA from various effluents, yet the specific molecular details remain unclear. In this study, based on laccase and BPA complex, three surfactants, cetyltrimethylammonium bromide (CTAB), sodium dodecylbenzene sulfonate (SDBS), and TritonX-100 (TX-100), were introduced to construct four systems. We applied MD simulation along with MM-PBSA method to investigate the effects of different surfactants on the binding of laccase with BPA. During the MD simulations, these three surfactants enveloped the enzyme surface to varying degrees, causing the solvent to separate from parts of the laccase surface. The addition of CTAB and SDBS suppressed BPA degradation mainly by influencing the polar solvation free energy and van der Waals (vdW) interactions between laccase and BPA. In contrast, TX-100 promoted the degradation of BPA by reducing polar solvation free energy. This explains why in the laccase-BPA complex system the addition of a certain concentration of TX-100 resulted in a higher degradation rate compared to CTAB or SDBS. Our work clarifies the molecular mechanisms of the interaction between laccase and BPA under the influence of CTAB, SDBS, and TX-100 surfactants, and provides some guidance for laccase degradation of BPA.

Synergistic effects of different ionic surfactants and temperature on rheological behavior and air-void structure of cement mortar

The influence of air entrainment on rheological behavior of fresh cementitious materials has attracted a lot of attention in the past years, but the results are still in controversy. In this research, cement mortars were prepared with equivalent air contents using different air-entraining admixtures (AEAs) to measure their fresh-state performance and hardened air-void system at variable temperature conditions, which aimed to clarify and unveil the coupled effects of different surfactants and temperature for the first time. The adsorption amount of AEA, zeta potential of cement, along with hydration kinetics of mixtures were evaluated to characterize the interaction of air bubbles with cement grains. It was found that for mixture without superplasticizer (SP), the impact of air entrainment on rheological parameters was dependent on the interaction intensity of AEA molecules with cement. For SP-plasticized mixture, air entrainment tended to cause a shear-thinning behavior with decreased plastic viscosity, while its influence on yield stress was in accordance with the situation without SP. The hardened samples with anionic surfactant contained more small voids and lacked big voids, whereas the samples with cationic surfactant showed opposite outcomes. With temperature decreasing, both the average chord length and the spacing factor of air voids increased owing to the reduced yield stress of mixture. The results will provide in-depth illustrations for understanding how air bubbles change the rheological behavior of mixture, and more importantly it will explain the seemingly inconsistent findings reported by previous literatures.

Molecular simulation study of the influence of different surfactants on the wetting characteristics of anthracite

The reduction of dust pollution in coal mines is of great importance both for protection of the environment and for the occupational safety and health of coal mine workers. The reduction of dust from anthracite has been a challenge due to its inherent hydrophobicity and high metamorphism. As a result, surfactants are commonly added to water to improve the wettability of coal, thereby improving the dust reduction efficiency of a water spray system. To clarify from a microscopic perspective the effect of different surfactants on the wettability of anthracite, models for the anthracite-surfactant-water system were established, and adsorption configuration, relative concentration distribution, and the diffusion coefficients of water molecules in the systems were thoroughly investigated with molecular simulations. The results showed the directional arrangement of surfactants in the simulation systems after 150 ps of equilibration, resulting in the reduced surface tension of the water-surfactant solution and enhanced wettability of anthracite. Along the (001) normal direction, the relative concentration of sodium dodecylbenzenesulfonate (SDBS) (15.32), the anthracite-water overlapping area, the diffusion rate of water molecules, and the activity (DSDBS = 0.97 × 10-8 m2·s−1) were maximized, indicating the excellent wettability effect of SDBS. The results of the study are of practical significance for improving the wetting effect of anthracite, improving the dust reduction efficiency, and safeguarding the occupational safety and health of personnel.

Influence of surfactant on clay swelling inhibition of weathered crust elution-deposited rare earth ores

Clay minerals are the main components of the weathered crust elution-deposited rare earth ores (WREOs), and their swelling properties have a significant effect on the safe and green in-situ leaching of WREOs. Few researches have been reported on the inhibition of clay swelling in WREOs and our teammates used combination of ammonium salts to suppress the clay swelling in previous work. Surfactants combined with (NH4)2SO4 were utilized as inhibitor in this study to reduce the amount of ammonium salts and thus decrease the ammonium pollution. Effects of different surfactants on inhibition of clay swelling were investigated, and the swelling inhibition mechanism was further discussed by DLVO theory. CTAB exhibited best performance among five surfactants. The swelling efficiency of kaolinite, halloysite and illite in DI water is 2.52%, 1.65% and 1.32% respectively, and these values can be reduced to 0.45%, 0.65% and 0.82% respectively in presence of single (NH4)2SO4. As (NH4)2SO4 was compounded with 0.04% CTAB, the swelling efficiency of kaolinite, halloysite and illite was further reduced to 0.25%, 0.45% and 0.31% respectively. The XRD and SEM analysis indicated that no change of the morphology and crystal structure of minerals after soaking with surfactants were presented. It was further clarified by DLVO theory that the London-van der Waals energy between clay particles increased, while both of the repulsion electrostatic energy and the total potential energy decreased in the presence of CTAB, and this was beneficial to the clay swelling inhibition.

Study on the mechanism of the influence of surfactant alkyl chain length on the wettability of anthracite dust based on EDLVO theory and inverse gas chromatography

The dispersion of coal dust on roadways adversely affects the productivity of coal mines and threatens the lives of mine workers. Accordingly, it is crucial to enhance the wettability of coal dust to improve its suppression efficiency. Herein, the mechanism of the influence of the surfactant alkyl chain length on the wettability of anthracite was investigated by systematically analyzing the degree of modification of anthracite with sodium dodecyl, tetradecyl, hexadecyl, and octadecyl sulfates using the “macroscopic + mesoscopic + microscopic + theoretical calculation” method. First, the differences in the macroscopic effects of different surfactants on modified anthracite were investigated via contact angle, settling time, and water retention rate experiments. It was concluded that surfactants with shorter alkyl chains exhibit a stronger ability to enhance the wettability of anthracite. Second, the mesoscopic characterization of different coal samples via laser particle size distribution, zeta potential, X-ray photoelectron spectroscopy, and inverse gas chromatography surface energy analyses revealed that the adsorption amount and intensity of surfactants on the anthracite surface increased with shortening surfactant alkyl chains owing to the spatial site resistance effect. Furthermore, molecular dynamic simulations of the microscopic molecular mechanism of adding different surfactants to enhance the wettability of anthracite showed that the interaction energy between coal dust and water molecules as well as the number of hydrogen bonds formed in the system rapidly increased with the shortening of the alkyl chains of anionic surfactants, which had a stronger binding ability to water molecules. Finally, the extended Derjaguin, Landau, Verwey, and Overbeek theory was employed to explain the relationship between the variation in electrostatic interaction, van der Waals, hydrophobic interaction, and total interaction energies and confirm that the wettability of anthracite particles increases with their dispersion in water. The ability of the surfactants to improve the wettability of anthracite increased at different degrees with the shortening surfactant alkyl chains. This study can provide breakthrough inspiration for the fields of coal flotation and haze control.

Montmorillonite swelling properties with various surfactants based on molecular simulation

The clay swelling is extremely harmful to the reservoir during tight oil and shale oil extraction. In order to prevent the interaction between clay and surfactants from making the clay to hurt reservoir during oil recovery, this paper studies the effects of different surfactants on reservoir clay. Clay-surfactant swelling experiments were conducted to observe the macroscopic effects of different surfactants on clay swelling and to summarize the rules, and molecular simulations were then used to explain this phenomenon. The results show that different surfactant groups have different tendencies to move toward the clay in water, with cationic groups moving toward the montmorillonite layers and anionic groups moving away from the montmorillonite layers, and nonionic does not have a significant effect. Cationic surfactant and amphoteric surfactant whose mechanism of inhibiting swelling action is directly reducing the negative electrical properties of the montmorillonite layers when Na+ outflow from montmorillonite layers, thus preventing electrostatic repulsion between montmorillonite layers to repel each other and move far away. In contrast, the nonionic surfactant, because it is not charged, cannot prevent the hydration of montmorillonite although there are surfactant molecules adsorbed on the layers due to van der Waals force; and the addition of anionic surfactant cannot suppress the negative electrical properties between the layers, which makes the diffusion of sodium ions between the layers augmented and promotes the swelling and dispersion of montmorillonite. This study is expected to provide benefits to oil production area by reducing the damage of surfactant imbibition fluid.

Molecular simulation of the regulation mechanism of the hydrophilic structure of surfactant on the wettability of bituminous coal surface

The regulation of surfactant on the wettability of bituminous coal surface is influenced by its hydrophilic structure. Based on the water absorption simulation and contact angle experiment of bituminous coal under different surfactants, the wetting effect of different surfactants with different hydrophilic structures on bituminous coal was obtained. The mechanism of different surfactants at the coal-water interface was analyzed by molecular dynamics simulation. The frontier orbital distribution and surface electrostatic potential distribution of surfactants and bituminous coal molecules were calculated by quantum chemistry method. The results showed that the wetting effect of surfactants on bituminous coal was APG1214 > OA-12 > SDBS > DTAB. The structure of hydroxyl and amine oxide made surfactants more conducive to promoting the interaction between coal and water molecules. The more oxygen and nitrogen elements the hydrophilic structure contains, the more favorable the surfactant is to modulate the wettability of the bituminous coal surface.

Non-ionic surfactant-assisted controlled release of oxyresveratrol on dendritic fibrous silica for topical applications

We present a simple and eco-friendly method for controlled drug release using a surfactant-assisted method. Oxyresveratrol (ORES) was co-loaded with a non-ionic surfactant onto KCC-1, a dendritic fibrous silica, using an ethanol evaporation technique. The carriers were characterized using FE-SEM, TEM, XRD, N2 adsorption–desorption, FTIR, and Raman spectroscopy, and the loading and encapsulation efficiencies were assessed using TGA and DSC techniques. Contact angle and zeta potential were used to determine the surfactant arrangement and the particle charges. To investigate the effects of different surfactants (Tween 20, Tween 40, Tween 80, Tween 85, and Span 80) on ORES release, we conducted experiments under different pH and temperature conditions. Results showed that the types of surfactants, drug loading content, pH, and temperature significantly affected the drug release profile. The percentage of drug loading efficiency of the carriers was in the range of 80 %–100 %, and the release of ORES was in the order of M/KCC-1 > M/K/S80 > M/K/T40 > M/K/T20 > MK/T80 > M/K/T85 at 24 h. Furthermore, the carriers provided excellent protection for ORES against UVA and maintained its antioxidant activity. KCC-1 and Span 80 enhanced the cytotoxicity to HaCaT cells, while Tween 80 suppressed the cytotoxicity.

Surfactant-assisted hydrothermal synthesis of large surface area nickel nanoparticles for electrochemical applications

A large surface area is an imperative parameter for electrocatalytic materials applied in electrochemical devices. In the present work, Ni nanoparticles were synthesized by hydrothermal method using three surfactants: sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and polyvinyl pyrrolidone (PVP) and two base media, i.e., sodium hydroxide (NaOH) and ammonium hydroxide (NH4OH). We investigated the effects of different surfactants and base mediums on Ni nanoparticles' crystallite size, particle size, and surface area. Experimental results revealed that Ni nanoparticles with smaller particle sizes (50–90 nm) and large surface area (28.4–64 m2/g) were obtained when NaOH was used as the base medium with all surfactants. Further, a high specific capacitance of 417 F/g, minimum charge transfer resistance of 490 Ω, and 91 % capacitance retention demonstrated that Ni nanoparticles obtained using PVP in NaOH could be applied as potential working electrode material in enhancing the performance of supercapacitor devices.

The effects of SDS, APG, and DTAB surfactants on the morphology of micro-nano RDX particles prepared in a microfluidic reactor

Abstract The effects of different surfactants on the morphology of 1,3,5-trinitro-1,3,5-triazinane (RDX) micro-nanoparticles prepared by solvent/non-solvent method in a microfluidic reactor were investigated. Alkyl polyglycoside (APG), sodium dodecyl sulphate (SDS) and dodecyltrimethylammonium bromide (DTAB) were selected as non-solvents. The surface tension and interfacial tension (IFT) properties of SDS, APG and DTAB were investigated. Compared to DTAB and SDS, the APG could effectively reduce the interfacial tension to 10−2 mN/m and exhibited better surface tension. The RDX prepared with different surfactants were analysed by scanning electron microscopy (SEM), X-ray diffractometry (XRD) and Fourier transform infrared spectrometry (FTIR). The results showed that the different surfactants could significantly improve the dispersion effect of RDX and the crystal morphology was uniform and stable.

Improved biocompatibility of anodized titanium implants by MnO nanoparticles

The surface addition of biocompatible metal oxide nanoparticles can significantly affect the physical, chemical, and biological properties of anodized titanium implants. Manganese is an important element for bone growth and regeneration and is essential for the body's vital systems. In this study, the biological properties of anodized titanium implants decorated with MnO nanoparticles were studied. At first, the effect of anodic oxidation voltage (15 V, 20 V, and 25 V) on the microstructure of titanium oxide nanotubes (TNTs) was investigated. Microstructural studies showed that the diameters of TNTs are increased by raising the applied voltage. Prepared TNTs with the applied voltage of 25 V exhibited a more uniform structure with an average inner diameter of 102 ± 15 nm. In the next step, MnO nanoparticles were synthesized through the thermal decomposition method. The effects of different surfactants, such as oleic acid and oleylamine, and various solvents, including dibenzyl ether and octadecene, on the size and morphology of the synthesized nanoparticles were studied. The results indicated that the MnO nanoparticles synthesized by dibenzyl ether solvent and oleic acid surfactant showed the smallest size and uniform morphology. Finally, the synthesized TNTs were decorated by the optimized MnO nanoparticles using the hydrothermal technique. X-ray diffraction (XRD) analysis was used to phase characterization. Microstructural studies were carried out by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analysis. MTT and cell morphology tests were carried out for the biocompatibility evaluation of the specimens. The results showed that the anodized titanium decorated with MnO nanoparticles indicated the highest cell viability compared to the anodized and untreated samples. Microstructural studies demonstrated that the cells attached to the surface and spreading of filopodia in the anodized titanium decorated with MnO nanoparticles are higher than the other samples.

Experimental Investigation of Cavitation Bulk Nanobubbles Characteristics: Effects of pH and Surface-Active Agents

Nanobubbles (NBs) have a widespread application in antimicrobial activity, wastewater treatment, and ecological restoration due to numerous peculiar characteristics, such as small diameter, long-term stability, and ability to produce hydroxyl radicals. Despite significant applications, only limited comprehensive investigations are available on the role of surfactants and pH in NBs characteristics. Therefore, this study examines the effects of different surfactants (i.e., anionic, cationic, and nonionic) and pH medium on bulk NB formation, diameter, concentration, bubble size distribution (BSD), ζ-potential, and stability. The effect of surfactant at concentrations above and below the critical micelle concentration was investigated. NBs were generated in deionized (DI) water using a piezoelectric transducer. The stability of NBs was assessed by tracking the variation in diameter and concentration over time. In a neutral medium, the diameter of NBs is smaller than in other surfactant or pH mediums. The diameter, concentration, BSD, and stability of NBs are strongly influenced by the ζ-potential rather than the solution medium. BSD curve shifts to a smaller bubble diameter when the magnitude of ζ-potential is high in any solution. In pure water, surfactant, and pH mediums, NBs have existed for a long time. NBs have a shorter life span in environments with a pH ≤ 3. Surfactant adsorption on the surface of NBs increases with increasing surfactant concentration up to a certain limit, beyond which it declines substantially. The Derjaguin-Landau-Verwey-Overbeek (DLVO) theory was used to interpret the NBs stability, resulting in a total potential energy barrier that is positive and greater than 45.55 kBT for 6 ≤ pH ≤ 11, whereas for pH < 6, the potential energy barrier essentially vanishes. Moreover, an effort has also been made to explicate the plausible prospect of ion distribution and its alignment surrounding NBs in cationic and anionic surfactants. This study will extend the in-depth investigation of NBs for industrial applications involving NBs.

Cationic surfactants influencing the enhancement of energy efficiency for perfluorooctanoic acid (PFOA) removal in the electrocoagulation-flotation (ECF) system

From an environmental perspective, approaching sustainability requires a fundamental conceptual shift from the wastewater treatment process toward integrated treatment systems that consider efficient and effective utilization. This study aims to investigate the effects of different surfactants on the removal of perfluorooctanoic acid (PFOA). We used cationic surfactants as both frothers and collectors in the electrocoagulation-flotation (ECF) method to improve the removal efficiency of PFOA. The results showed that, under a monopolar aluminum electrode and with an initial PFOA concentration of 0.25 mM, the ECF method with decyl-trimethyl-ammonium bromide (DTAB) was able to remove over 98% of PFOA within 10 min. Cationic surfactants with a similar linear alkyl chain shape to PFOA, but a longer chain length, are more effective at removing PFOA through the ECF process. The removal mechanism is thought to involve co-precipitation with aluminum hydroxides through Al–F bonding, co-flotation with cationic surfactants, and mixed micelle formation with cationic surfactants. The optimal conditions were tested in both synthetic and realistic wastewater matrices and produced similar results. It has the potential for real wastewater application. The energy yield (G50) of ECF with 5 mM DTAB is 497 g·kWh−1, superior to other treatments, and is an extremely energy-effective method for separating PFOA from wastewater.

Experimental investigation on pH and stability of distilled water ethylene glycol mixture with graphene nanoplatelets

An efficient heat transfer medium improves the overall efficiency of the equipment, and the main difficulty is with making well-dispersed nanoparticles in base fluids. The current research is focused to study the effect of different surfactants on nanoparticle dispersion and enhancement through property modifications. The stability and pH value of various surfactants with varying sonication duration were studied and compared with the graphene nanofluids. The graphene nanofluids were prepared by a two-step method by dispersing 0.1 wt% graphene nanoparticles in distilled water and ethylene glycol with a ratio of 70:30. The surfactants namely Cetyltrimethylammonium bromide (CTAB), Polyvinylpyrrolidone (PVP K-30), and Polysorbate 60 (Tween 60) of each 0.1 wt% were used for stabilizing the nanofluids. The duration of the sonication process was set as 60, 90, and 120 min respectively followed by the magnetic stirring for 60 min duration. The stability behavior of nanofluids was studied through visual inspection, UV spectrum, and zeta potential techniques, and the corresponding pH values were measured to correlate with the performance of the heat transfer equipment. The results showed that the dispersion of graphene nanofluids strongly depends on the type and amount of dispersant in the absolute value of zeta potential. Finally, the optimum conditions were found based on the enhanced stability, pH, and sonication time of graphene nanoplatelets in distilled water-ethylene glycol mixture with Polyvinylpyrrolidone (PVP K-30) as a surfactant for the battery thermal management systems (BTMS) in electric vehicles.

Research Trends on the Dispersibility of Carbon Nanotube Suspension with Surfactants in Their Application as Electrodes of Batteries: A Mini-Review

In the battery field, carbon nanotubes (CNTs) attract much attention due to their potential as a supporting conducting material for anodes or cathodes. The performance of cathodes or anodes can be optimized by introducing densely packed CNTs, which can be achieved with high dispersibility. The efficiency of CNT usage can be maximized by enhancing their dispersibility. An effective technique to this end is to incorporate surfactants on the surface of CNTs. The surfactant produces a surface charge that can increase the zeta potential of CNTs, thereby preventing their agglomeration. Additionally, surfactants having long chains of tail groups can increase the steric hindrance, which also enhances the dispersibility. Notably, the dispersibility of CNTs depends on the type of surfactant. Therefore, the results of dispersibility studies of CNTs involving different surfactants must be comprehensively reviewed to enhance the understanding of the effects of different surfactants on dispersibility. Consequently, this paper discusses the effect of different types of surfactants on the dispersibility of CNTs and presents several perspectives for future research on dispersibility enhancement.

Influence of Different Surfactants on Carbon Fiber Dispersion and the Mechanical Performance of Smart Piezoresistive Cementitious Composites

This experimental study presents the effect of different surfactants on micro-scale carbon fiber (CFs) distribution into carbon fiber reinforced cement-based composites (CFRC) in terms of flexural and compressive strength, stiffness, flexural toughness, and strain-sensing ability. Conducting a narrative review of the literature focusing on the fibers’ separation, this paper follows a methodology introducing a combination of mechanical and chemical carbon fibers dispersion, as well as the different mixing processes (wet or dry). Three types of surfactants: Carboxymethyl cellulose (CMC), cellulose nanocrystal (CNC), and superplasticizer (SP), were applied to evaluate the CFs distribution in the cement paste matrix. Compressive and flexural strength, modulus of elasticity, and ductility of the cement-based composites (CFRC) reinforced with 0.5 wt.% CFs were investigated by three-point bending and compressive tests; flexure tests were also conducted on notched 20 × 20 × 80 mm specimens using the Linear Elastic Fracture Mechanics (L.E.F.M.) theory. Moreover, the electrical conductivity and the piezoresistive response were determined by conducting electrical resistance measurements and applying compressive loading simultaneously. The results clearly reveal that the CFs/SP solution or the CFs’ dry incorporation led to a significant enhancement of flexural strength by 32% and 23.7%, modulus of elasticity by 30% and 20%, and stress-sensing ability by 20.2% and 18.2%, respectively. Although the wet mixing method exhibits improved mechanical and electrical conductivity performance, constituting an adequate strain and crack sensor, the authors propose dry mixing as the most economical method, in addition to the enhanced mechanical and electrical responses. The authors recommend an effective method for structural health monitoring systems combining an economical CFs insertion in cementitious smart sensors with great mechanical and self-sensing responses.

Effects of different surfactants on the conjugates of soybean protein-polyphenols for the preparation of β-carotene microcapsules.

In this study, we investigated the spray-drying microencapsulation of β-carotene in oil co-stabilized by soy protein isolate-epigallocatechin-3-gallate conjugate (SPE) and small molecule surfactants [sodium dodecyl sulfate (SDS), hexadecyl trimethyl ammonium bromide (CTAB), and tea saponin (TS)] of different concentrations [0.1, 0.5, and 1.0% (w/v)], as a prospective approach to stabilize β-carotene. The results show that different surfactant types and concentrations significantly affect the encapsulation efficiency, water dispersibility, microstructure, and digestion of the microcapsules. Interactions between the surfactants and the SPE at the interface were found to include both synergistic and competitive effects, and they depended on the surfactant type and concentration. Moreover, the addition of SDS and TS before spray drying significantly improved the microencapsulation performance of the microcapsules and the water dispersion behavior of the corresponding spray-dried powders. The highest encapsulation efficiency was achieved for the SPE-0.1TS-encapsulated β-carotene microcapsules. In contrast, the addition of CTAB was not conducive to microcapsule formation, resulting in poor encapsulation efficiency, water dispersibility, thermal stability, β-carotene retention rate, and oxidation stability. In vitro gastrointestinal digestion results revealed that the addition of CTAB promotes the release of β-carotene and improves the bioaccessibility of β-carotene. In contrast, except for SPE-1.0SDS, the addition of SDS and TS inhibited β-carotene release and reduced β-carotene bioaccessibility. This study demonstrated that this novel β-carotene encapsulation formulation can overcome stability limitations for the development of β-carotene supplements with a high bioaccessibility.

Impact of Surfactants on the Electrical and Rheological Aspects of Silica Based Synthetic Ester Nanofluids

This study reports experimental investigations of the effects of different surfactants (CTAB, Oleic acid and Span 80) on silica based synthetic ester nanofluids. The positive and negative potential observed for the ionic (CTAB) and non-ionic surfactant (Span 80) from zeta potential analysis indicates an improved stability. The optimization of nanofillers and surfactants is performed considering the corona inception voltage measured using ultra high frequency (UHF) technique and fluorescent fiber. Rheological analysis shows no significant variation of properties with shear rate, implying Newtonian behavior even with the addition of surfactant. In addition, the permittivity of the nanofluid is not much affected by adding surfactant but a marginal variation is noticed in the loss tangent with the effect of temperature. The fluorescence spectroscopy shows no change in the emission wavelength with the addition of silica nanofiller and surfactants. Flow electrification studies indicate an increase in the streaming current with the rotation speed and temperature, with a higher current magnitude observed in the case of nanofluids.

Effect of anionic/nonionic surfactants on the wettability of coal surface

To study the effect of different surfactants on the wettability of coal surface, the adsorption simulation of different coal-surfactant-water model systems was carried out by using materials Studio 8.0 molecular simulation software. Combined with the contact angle experiments between different surfactants and coal samples, the effect law of different surfactants on the wettability of three coal samples was obtained. The adsorption simulation results were analyzed from the aspects of adsorption spacing, adsorption sites and “reverse adsorption” phenomenon, and the mechanism of the influence of different surfactants on the wettability of coal surface was revealed from a microscopic point of view. The research results show that: the higher the degree of coal metamorphism, the lower the water absorption and the worse the wettability of coal. Anionic surfactant SDBS has better effect on improving the wettability of Hami (HM) coal with low metamorphic degree, while nonionic surfactant AEO9 has better effect on improving the wettability of Yuwu (YW) and Tunliu (TL) coal with high metamorphic degree. By comparing intermolecular distances, it is shown that nonionic surfactants are more likely to aggregate on the surface of coal molecules and have a greater effect on the wettability of the coal surface. The middle position of the benzene ring structure of coal is the best adsorption site for the hydrophobic tail of the surfactant. By calculating the adsorption energy of different simulation systems, it is confirmed that the phenomenon of “reverse adsorption” between nonionic surfactants and low metamorphic coal is caused by hydrogen bonding. The results of the study provide a theoretical basis for the effective application of different surfactants in coal dust control.

Effects of different surfactants on the degradation of petroleum hydrocarbons by mixed‐bacteria

AbstractBACKGROUNDSurfactant‐enhanced remediation (SER) has been widely applied to remove petroleum hydrocarbon (PH) pollutants, but there are few studies on the mechanism through which surfactants affect the hydrocarbon metabolite ability of microorganism.RESULTSIn this work, combination bacteria and surfactant were selected to remove PH, and the degradation bottleneck concentration of single‐bacteria was 10 g L–1 according to the PH degradation rate. However, the degradation efficient of mixed‐bacteria was further increased after adding surfactants. Among them, the PH degradation rate of Kocuria rosea + Bacillus odyssey and Microbacterium. sp + B. odyssey at the bottleneck concentration had been respectively reached to 81.58 ± 6.29% with tween‐80 and 88.35 ± 7.58% with rhamnolipid. Compared with no surfactant, the relative abundance of global overmaps, amino acid metabolism, and carbohydrate metabolism was increased in adding tween‐80 condition. However, when rhamnolipid was added, the relative abundance of ABC transporters, two‐component system, and bacteria chemotaxis was clearly increased, indicating an improvement of transportation, absorption, and degradation of PH. Additionally, the gene abundance of alkB and nah was also significantly increased with above condition. Meanwhile, the gene abundance of alkB and nah was also significantly enhanced by above condition.CONCLUSIONThis study offers new insights into the functional changes of mixed‐bacteria during PH degradation in different surfactant‐enhanced systems. © 2021 Society of Chemical Industry (SCI).